Colon target microencapsulation by a dual process combining emulsification followed by complex coacervation: Viability of microencapsulated probiotics under simulated gastrointestinal and storage conditions

Abstract

In Chapter 1, proteolytic probiotic strains were isolated from fermented products, kimchi in Korea, and kumis in Mongolia. To confirm the probiotic characteristics of the isolated strains, bile salt and acid tolerance were measured, showing survival rates of over 84% and 68% in both bile salt and acid conditions. The two probiotics with the highest extracellular proteolytic activity, measuring 25.7 U/mg and 27.8 U/mg, were identified, and examined for safety aspects. The selected two lactic acid bacteria (LAB) strains isolated from kimchi and kumis were identified as L. pentosus and L. plantarum, respectively, through 16S rRNA sequence analysis. Furthermore, these strains demonstrated the capability to tolerate the conditions within the gastrointestinal tract, low pH, and heat treatment. Therefore, L. plantarum and L. pentosus proved to be the most attractive for further study, confirming the safety and exceptional effectiveness of the specifically proteolytic probiotics. In Chapter 2, the soy protein isolate (SPI) with arabic gum (GA) or pectin (PEC) produces coacervated emulsions containing probiotics. The optimal conditions for SPI (2.5%, w/v) and GA/PEC (2.5%, w/v) coacervation were determined as 80:20 (SPI/GA and SPI/PEC) at pH 4.0. Dual emulsions (DE) and multilayer emulsions (ME) were prepared by coating DE with chitosan (CS) and alginate (Al) under optimized conditions. The encapsulation efficiency for all microcapsules was over 88%. Coacervated ME demonstrated increased survival rates in the stomach, small intestine, and colon environments compared to free probiotics, approximately 1.3, 1.5, and 2.8 times higher, respectively. Furthermore, coacervated ME effectively protected probiotics from acidic pH and heat treatments compared to free and DE-microencapsulated probiotics. In Chapter 3, the freeze-dried microencapsulated probiotics were evaluated for survival under different storage conditions to assess their applicability in food. The microencapsulated probiotic powder maintained a survival rate of over 10^6 CFU/g after 28 days of storage at 4°C and 25°C, indicating its suitability for dry product applications. Furthermore, in a buffer system at pH 4.0, the microencapsulation significantly increased viable cells compared to free cells (p< 0.05). In addition, the study assessed the effect of supplementing orange juice with free and microencapsulated L. plantarum on the physicochemical characteristics and probiotic viability for storage at 4˚C for 28 days. Microencapsulation significantly improved the viable cells, almost 2 times higher than those in the free L. plantarum (p< 0.05). These results suggest that it is possible to produce probiotic-supplemented orange juice with suitable quality parameters and enough viable probiotics.